Free piston engine



2 Sheets-Sheet l Filed March 5, 1961 IN V E N TOR Haro/o Kosof Jan. 21, 1964 H, KosoFF 3,118,434

FREE PIsToN ENGINE Filed March s. 1961 2 sheets-sheet 2 IN VEN TOR Haro/0 KOSOJQ( United States Patent O 3,118,434 FREE PISTQN ENGINE Harold Kosolf, 1203 Hale St., Philadelphia 11, Pa. Fires Mai. s, 196i, ser. No. 93,094 lil Claims. (Ci. 12S-46) This invention relates to a means of regulating and maintaining the outward limit of piston motion in a free piston engine.

In the free piston engine it is necessary that the most outward limit of piston motion have both a higher and a lower bound. Hitherto, this has been accomplished by means of mechanical linkage which operatively connects the piston with a fuel metering device. It is the purpose of this invention to eliminate this linkage and to maintain bounds on piston motion by means of .a novel arr-angement of a piston position sensing device and an associated servomotor in connection with a fuel meter or air throttle. i

Another feature of this invention is means by which the most outward position of the power piston may be varied by means of variation in the operative conditions in associated conduits.

Another feature of this invention is the means by which power piston outstroke in the free piston engine having no synchronizing mechanical linkage may be regulated. Reference is made to a `co-pendinig application, Serial Number 76,933, filed December 19, 1960; by this inventor.

Other objects and advantages will be apparent from the speciiieation and claims and from the accompanying drawings which illustrate the embodiment of this invention.

FIGURE l is a part sectional View of the free piston engine showing the piston position sensing device, associated conduits, a servomotor, and a fuel meter/injector relative to the engine.

FIGURE 2 is a part sectional view :and shows the combustion chamber, part of the pump chambers, fuel supply system, and part of the power pistons of a free piston engine; `and a pneumatic embodiment of this invention.

Refer to FIGURE l. The free piston engine shown includes a combustion chamber 1, two pump chambers 2, two rebrounce chambers 3, two power pistons 4, intake port 5, eX-haust pont i6, and fuel meter/injector '7. At the time of combustion, the combustion chamber pressure causes the pistons to move toward a mos-t outward position. Energy stored in the compressed rebounce chambers restores the pistons to a most inward position and provides the energy for pumping the iluid within the pump chambers. It is necessary for satisfactory operation that the most outward piston position be sufficient to allow replenishment of the :combustion chamber with fresh charge via the intake port and exhaust port. Also, it is necessary that the most outward position be less than that which would remove the pistons entirely from the combusti-on chamber.

By Varying the fuel rate of an operative engine the outer limit on piston motion maybe adjusted; an increase in the fuel rate will cause a corresponding increase in the combustion chamber pressure and outstroke of the pistons, and conversely, a decrease in the fuel rate will cause a 'corresponding decrease in the combustion chamber pressure and foutstroke of the pistons. In the preceding manner the outer limit of piston motion may be maintained near a nominal value.

ln an yoperative `free piston engine the above principles are implemented by connecting to the engine a piston position sensing device 1d which communicates with a servomotor 1'1 via conduit 12. In turn, the servomotor is operatively connected to a fuel meter/injector 7 in operative connection with a fuel supply 13. If in an 3,ll,434 Patented Jan. 21, i964 ICC openative engine the sensing device senses a greater' than nominal outstroke of the piston, a signal is sent to the servomotor which in turn moves by means of link 14 the fuel meter to a position off lessened fuel rate. And conversely, Ifor less than nominal outstroke, the sensing device sends a signal to the servomotor to increase the fuel rate.

The piston position sensing device senses the position of the piston by sensing a discontinuity of the piston. Each piston has at least two discontinuities; a left face and a right face. Also, discontinuities of the piston may be a groove, dissimilar material, etc., existent between the left and right face. The sensing device is positioned relative to the discontinuity such .that during steady state engine ope-nation, on the piston outstroke the discontinuity will btu-t slightly pass the sensing device. During the time the discontinuity is beyond the sensing device a signa-l is emitted by the sensing device. During the time the discontinuity is not Ibeyond the sensing device either no signal or a signal of the opposite polarity is emitted; if no signal is emitted a small restoring force or signal is continuously applied tothe servomotor. The sensing device may either be a simple ori/off type, or it may emit a signal proportionate to the time lapse between two consecutive crossings as the discontinuity passes the sensing device.

yThe sensing device may be an electrical contact which is kept grounded against the side of the piston. When the piston passes the contact near the end of the piston outstroke, the contact is broken and remains broken until the piston passes the contact on the instroke. The voltage in the circuity associated with the contact will rise during the time that the contact is broken. This higher voltage or signal acts on the servomotor which then in turn causes the lfuel rate to drop, and thus, reduces the piston outstroke. A small restoring force on the servomotor or current into the associated circuitry causes the servomotor to slowly increase the -fuel rate and thus the extent of piston outstro-ke. To offset this slow increase in fuel nate, the contacts are opened slightly during a majority of the engine cycles. Hence, the ou-ter limit of the piston motion is kept within close bounds.

A pneumatic means likewise senses the passing of the piston discontinuity across the sensing device. In this case the sensing device is a vent. Exposure of the vent to an engine chamber containing fluid pressure causes the pressure in the conduit system in communication with the vent to chan-ge. This change is transmitted to a servomotor for purposes of changing the fuel nate. A small orice communicates the conduit system 'with -a second cham-ber which is at `a different pressure from the iirst chamber. The magnitude of pressure necessary for operation of the servomotor is between the magiitude of pressure in the first and second chamber. To offset the change of pressure acting on the servomotor caused by the action of the small orifice, the vent is exposed slightly during a majority of cycles. Hence, the outer limit of piston moiton is main-tained within close bounds.

Refer to FIGURE 2. ln this particular embodiment pneumatic devices are the instruments by which this invention is implemented. Small orifice 2d communicates the bellows servomotor 11 with a fluid receiver 2l via conduit 27. Vent 22 via conduit Z3 communicates the bellows servomotor with a fluid source l', which in this illustration is the combustion chamber. The vent is connected to the combustion chamber at a point near the end of the pistons combustion stroke. FIGURE 2 shows the pistons at a nominal most outward position. The fuel meter/injector '7' is operatively connected to the servomotor by a link 24'. In this illustration the servomotor is a flexible bellows having an appropriate spring rate and operative force. Conduit 2S connects the fuel meter/injector with a fuel supply. Conduit 26 connects the fuel meter/injector with a source of operative energy. Plus direction of link motion will increase the fuel rate; minus direction of link motion will decrease the fuel rate.

The pressure associated with the servornotor is increased by means of an intermittent flow of uid into the servomotor via the vent. r[his pressure is decreased by means of a continuous ow of fluid from the servomotor via the small orifice. Since the vent is opened intermittently, it is necessarily much larger than the orifice. Corresponding to a net zero ow through the servomotor, i.e., flow in equals iiow out, is a nominal vent exposure and outer limit of piston motion. If the outer limit of piston motion is not of a nominal value, there will be a non-zero flow of fluid through the servomotor and a consequent change of servomotor pressure. Greater than nominal outward piston motion will cause a greater than nominal vent exposure to the combustion chamber and a consequent increase in the pressure associated with the servomotor. The increased pressure in the servomotor l in turn cause a decrease in the fuel rate which will in turn decrease the most outward piston position. And conversely, less than nominal outward piston motion will cause a less than nominal vent exposure to the combustion chamer and a consequent decrease in the pressure associated with the servomotor. The decreased pressure in the servomotor will in turn cause an increase in the fuel rate which will in turn increase the most outward piston position. In the aforedescribed manner the engine will converge toward and maintain an outer limit of piston motion within operative bounds.

Since the pistons in an operative engine need by synchronized, sensing the position of one piston is equivalent to sensing the position of all pistons. By using a constant pressure fluid source and a constant pressure fluid receiver the outer limit of piston motion may be maintained constant and independent of the engines operative conditions. By using iiuid sources and/or receivers whose pressure is functionally related to the operative conditions in the engine, the outer limit of piston motion may be varied as a function of the operative conditions of the engine.

it is understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departing from its spirit as defined in the following claims.

What I claim as my invention and desire to secure by Letters Patent is:

l. In an internal combustion of the free piston type, the combination comprising a power cylinder, at least one power piston adapted to reciprocate within said power cylinder, at least one pump chamber defined in part by extensions of said power piston and said power cylinder, at least one rebounce device, means operatively associated with said power piston for compressing elastic material of said rebounce device on the combustion stroke of said power piston, the energy in said compressed elastic material driving the power piston on the compression stroke; a fuel meter in operative connection to a fuel supply for admitting fuel to said cylinder, a servomotor in operative connection to said fuel meter, a power piston position sensing means aiixed to and penetrating said power cylinder such that the position of said power piston is directly sensed, said position sensing means being in operative connection with said servomotor to affect the fuel rate of said engine in response to the most outward position of said power piston.

2. In an internal combustion engine of the free piston type, the combination comprising a power cylinder, at least one power piston adapted normally to reciprocate within specified bounds within said power cylinder, at least one pump chamber defined in part by extensions of said power piston and said power cylinder, at least one rehounce device, means operatively associated with said power piston for compressing elastic material of said rebounce device on the combustion stroke of said power piston, the energy in said compressed elastic material driving the power piston on the compression stroke; a fuel meter in operative connection with a fuel supply for admitting fuel to said chamber, a servomotor in operative connection to said fuel meter, a power piston position-sensing means affixed to and penetrating said power cylinder such that thc position of said power piston is directly sensed, said position sensing means being in operative connection with said servomotor to increase the fuel rate of said engine when said power piston on the combustion stroke does not pass a specified sensed point within said cylinder and to decrease said fuel rate of said engine when said power piston on the combustion stroke does pass a specified sensed point within said cylinder.

3. in an internal combustion engine of the free piston type, the combination comprising a power cylinder, at least one power piston adapted normally to reciprocate within specified bounds within said power cylinder, at least one pump chamber defined in part by extensions of said power piston and said power cylinder, at least one rebounce device, means operatively associated with said power piston for compressing elastic material of said rebounce device on the combustion stroke of said power piston, the energy in said compressed elastic material driving the power piston on the compression stroke; a fuel meter in operative connection with a fuel supply for admitting fuel to said cylinder, a servomotor in operative connection to said fuel meter, said servomotor being pressure responsive, said servomotor also being constructed and arranged to have said pressure decreased by means of a small orifice which maintains communication between said servomotor and a fluid receiver, and further, a vent penetrating said power cylinder, and so positioned that when said power piston on the combustion stroke does pass a specified sensed point within said cylinder, said pressure is increased by virtue of the consequent communication between said servomotor and a fluid source.

4. In an internal combustion engine of the free piston type, the combination comprising a power cylinder, at least one power piston adapted normally to reciprocate within specified bounds within said power cylinder', at least one pump chamber defined in part by extensions of said power piston and said power cylinder, at least one rcbouncc device, means operatively associated with said power piston for compressing elastic material of said rebounce device on the combustion stroke of said power piston, the energy in said compressed elastic material driving said power piston on the compression stroke; a fuel meter in operative connection with a fuel supply for admitting fuel to said cylin- "er, a servomotor in operative connection to said fuel meter, said servomotor being pressure responsive, said servomotor also being constructed to have said pressure increased by means of a small orifice which maintains communication between said servomotor and a fluid source, and further, a vent penetrating said power cylinder and so positioned that when said power piston on the combustion stroke does pass a specified sensed point within said cylinder, said pressure is decreased by virtue of the consequent communication between said scrvomotor and a fluid receiver.

5. In an internal combustion engine in which at least one piston is arranged for movement within a cylinder and wherein said cylinder and at least part of said piston cooperate to define a combustion chamber to which fuel is applied, the improvement consisting of means directly sensing the movement of said piston for adjusting the rate at which said fuel is applied to said combustion chamber, said fuel-rate adjusting means including means substantially in contact with a surface of said piston.

6. In an internal combustion engine in which at least one piston is arranged for movement within a cylinder and wherein said cylinder and at least part of said piston cooperate to define a combustion chamber to which fuel is applied, the improvement consisting of means directly sensing the movement of said piston for adjusting the rate at which said `fuel is applied to said combustion chamber, said fuel-rate adjusting means including an aperture in a wall of said cylinder -adjacent a surface of said piston.

7. The invention according to claim 6 wherein said aperture is in a portion of said cylinder Wall which partially denes said combustion chamber and is arranged to communicate therewith approximately at the end of each outstroke of said piston thereby to transmit pressure developed in said combustion .chamber to said adjusting means.

8. In an internal combustion engine in which at least one piston is arranged for movement Within a cylinder and wherein said cylinder and at least part of said piston cooperate to dene a combustion chamber to which `fuel is applied, the improvement consisting of means directly responsive to the movement of said piston for adjusting the rate at which said lfuel is applied to said combustion chamber, said fuel-rate adjusting means comprising:

(a) an aperture in said cylinder wall past which said piston moves, and

(b) means including a pressure-responsive device coupled to said aperture and constructed to Vary the amount of fuel supplied to said combustion chamber as a function of the pressure developed in said valve.

9. The fuel-rate adjusting means according to claim 8 with the addition of (c) means in said device constructed to permit the escape of amounts of pressurized elastic material therefrom which are yvery small compared to amounts of said material applied thereto via said aperture.

10. The fuel-rate adjusting means according to claim 9 wherein said aperture is located in said combustion chamber and is located so as to permit pressure developed therein to be applied to said device substantially toward the end of the outstroke of said piston and further wherein said (c) means comprises a Very small orifice in said device arranged to communicate with a lfluid receiver.

References Cited in the rile of this patent UNITED STATES PATENTS 2,083,680 Anderson et al. lune 5, 1937 2,132,083 Pescara Get. 4, 1938 2,200,892 Pescara May 14, 1940 2,246,701 Steiner June 24, 1941 2,425,850 Welsh Aug. 19, 1947 2,481,927 Hooker Sept. 13, 1949 2,943,438 f Huber July 5, 1960 2,976,860 Bayer Mar. 2-8, 1961 2,983,098 Bush May 9, 1961 2,991,772 Young June 11, 1961 FOREIGN PATENTS 218,708 Switzerland Apr. 1, 1942 

1. IN AN INTERNAL COMBUSTION ENGINE OF THE FREE PISTON TYPE, THE COMBINATION COMPRISING A POWER CYLINDER, AT LEAST ONE POWER PISTON ADAPTED TO RECIPROCATE WITHIN SAID POWER CYLINDER, AT LEAST ONE PUMP CHAMBER DEFINED IN PART BY EXTENSIONS OF SAID POWER PISTON AND SAID POWER CYLINDER, AT LEAST ONE REBOUNCE DEVICE, MEANS OPERATIVELY ASSOCIATED WITH SAID POWER PISTON FOR COMPRESSING ELASTIC MATERIAL OF SAID REBOUNCE DEVICE ON THE COMBUSTION STROKE OF SAID POWER PISTON, THE ENERGY IN SAID COMPRESSED ELASTIC MATERIAL DRIVING THE POWER PISTON ON THE COMPRESSION OF SAID POWER PISTON, THE ENERGY IN SAID COMPRESSED ELASTIC MATERIAL DRIVING THE POWER PISTON ON THE COMPRESSION STROKE; A FUEL METER IN OPERATIVE CONNECTION TO A FUEL SUPPLY FOR ADMITTING FUEL TO SAID CYLINDER, A SERVOMOTOR IN OPERATIVE CONNECTION TO SAID FUEL METER, A POWER PISTON POSITION SENSING MEANS AFFIXED TO AND PENETRATING SAID POWER CYLINDER SUCH THAT THE POSITION OF SAID POWER PISTON IS DIRECTLY SENSED, SAID POSITION SENSING MEANS BEING IN OPERATIVE CONNECTION WITH SAID SERVOMOTOR TO AFFECT THE FUEL RATE OF SAID ENGINE IN RESPONSE TO THE MOST OUTWARD POSITION OF SAID POWER PISTON. 